Drug or fluid delivery devices such as drug pumps are known. Drug pumps often are grouped into types such as so-called ambulatory pumps, peristaltic pumps, syringe pumps, gravity-feed pumps, elastomeric pumps, and multichannel pumps. Although these groupings are often helpful for a general understanding and characterization of drug pumps per se, such terminology is neither limiting nor conclusive and may at times be used interchangeably and variably in the medical arts.
Ambulatory infusion pumps are portable drug or fluid delivery devices that are used to deliver drugs or fluids typically including, but not limited to: therapeutic agents; nutrients; drugs; medicaments such as antibiotics, blood clotting agents, and analgesics; and other fluids to a patient, typically for purposes of treating physiological and other medical conditions. The devices can be used to introduce the drugs or fluids into patients' bodies utilizing any of several routes such as intravenously, subcutaneously, arterially, or epidurally. Such devices may also provide a so-called PCA (or, “patient controlled analgesia”) function, depending upon a particular medical need.
Ambulatory infusion pump assemblies generally include: a control module with a pumping mechanism and an interface for programming of the pump by a healthcare practitioner or patient; a cassette releasably connected to the control module; a reservoir, bag, or other container with the cassette which contains the fluid to be delivered; and an infusion set or fluid line containing an assembly of tubing, luers, connectors, valves, cannulae, or the like for delivering the fluid from the cassette to the patient. A patient receives a dose of medication or other fluid by activation of a control on, or connection to, the control module such as a push-button activator or switch, or in some embodiments via a remote dose cord or an automatic, computerized program. Such activation starts the pumping mechanism in the pump which delivers a measured dose of the fluid from the reservoir, bag, or other container (collectively herein, “reservoir”) in the cassette to the patient via the fluid line within an allowable time interval as programmed.
When a reservoir is emptied, the cassette is released from the pump and the depleted reservoir is removed from the cassette for disposal—or the entire cassette is disposed. A new or refilled reservoir is placed into the cassette, or a new cassette is obtained; and the cassette is then remounted to the control module. When the fluid line has been primed, the pump can then be restarted to continue infusion or delivery of the fluid to the patient.
The cassette reservoir typically comprises a bag formed from a flexible polymer material that is sealed at its edges, in contrast to a relatively rigid material such as glass or hard plastic, for ease of manufacture and handling. However, it has been found that pumping a flexible reservoir to a completely empty state can be challenging. This may happen particularly when using a vacuum to draw a viscous fluid from the reservoir, because the typically flexible reservoir can collapse as it empties, sealing off pockets of fluid that are thus largely inaccessible for delivery to the patient. This can result in a false or premature signal of an empty reservoir, or inconsistent metering and delivery of the remaining fluid to the patient. This is especially a concern when the fluid being delivered is of high value such that it is desired to minimize or eliminate any waste, or if consistent metering and delivery of the fluid to the patient is highly critical in order to avoid over- or under-dosing.
Known systems and methods for addressing these issues may be highly complex—which may likely make such a pump more costly—or may be difficult or impossible to remedy, thereby likely requiring replacement of at least a part of the pump assembly. Therefore, it would be particularly useful and advantageous to provide a fluid delivery device including a cassette and reservoir assembly that is capable of satisfactory emptying of the reservoir.